1. Field of the Invention
The present invention relates to a PVD cylindrical target used for a PVD process (Physical Vapor Deposition) such as sputtering or vacuum arc deposition.
2. Description of the Related Art
Conventionally known arts include, for example, a PVD cylindrical target having an evaporation material such as Cr bonded (sintered) to the outer circumferential surface of a cylindrical substrate consisting of Fe or stainless material by hot isostatic pressing (HIP) process. In this kind of PVD cylindrical targets, cracking or peeling is frequently caused between the evaporation material and the substrate since the substrate is constricted more largely than the evaporation material in a temperature-lowering process of the HIP treatment by a difference in thermal expansion coefficient (thermal expansion rate) between the substrate and the evaporation material. This phenomenon is hardly actualized in a PVD cylindrical target having a relatively small total length or diameter, but is conspicuous in a large PVD cylindrical target.
When such a PVD cylindrical target is used in incorporation into, for example, a PVD equipment, slippage resulted from the above-mentioned difference in thermal expansion coefficient occurs between the substrate and the evaporation material in the axial direction of the PVD cylindrical target in accordance with temperature rise during use, disabling the use thereof.
To solve this problem, for example, a PVD cylindrical target disclosed in Japanese Patent Application Laid-Open No. 7-173622 is adapted to suppress axial slippage between the both by forming a protruding part or recessed part on the outer circumferential surface of the substrate.
Further, PVD cylindrical targets disclosed in Japanese Patent Laid-Open No. 9-195039 and Japanese Patent Laid-Open No. 5-230645 are adapted to suppress peeling or cracking between the substrate and the evaporation material by interposing an intermediate layer for suppressing diffusions of the evaporation material and the substrate between the both.
However, when the PVD cylindrical targets of the above-mentioned Japanese Patent Laid-Open No. 9-195039 and Japanese Patent Laid-Open No. 5-230645 are formed using, as the evaporation material, a material consisting of two or more kinds of elements such as CrB, which has an extremely small thermal expansion coefficient, compared with Fe constituting the substrate or Ni or the like used as the intermediate layer, an extremely large stress is left within the PVD cylindrical target after HIP treatment or during PVD work due to the thermal expansion difference between the materials, causing the cracking or peeling of the evaporation material.
Further, since the material such as CrB is extremely brittle, the protruding part or recessed part having a sharp angular portion as described in Laid-Open No. 7-173622 is possible to easily cause cracking or peeling of the evaporation material by the concentration of stress to the angular portion.